1. Field of the Invention
The present invention provides a projection system. In particular, the projection system utilizes a digital micromirror device to switch between two light source modules.
2. Descriptions of the Related Art
With the rapid development of science and technology, information display technology has been advancing at a fast pace and, accordingly, projectors have become increasingly popular as well. In addition to the more frequent use in offices and meeting rooms, projectors have also gradually become an indispensable household appliance for entertainment. Among projectors employing various display technologies, digital light processing (DLP) projectors that employ core technology and elements from Texas Instruments Inc., U.S. have gradually become the mainstream product due to advantages such as high contrast ratio, small volume and light weight. In an effort to improve the reliability of the projectors, extend the service life of the light sources and increase the display luminance, a dual-light-source module comprising two light sources that are switched alternately according to a time sequence has been proposed in the art to improve the display quality of the DLP projectors.
As shown in FIG. 1, a projection apparatus 1 of the prior art is depicted therein. The projection apparatus 1 comprises a light source system 11 and an imaging system 13. The light source system 11, which is adapted to provide light beams necessary for imaging, comprises a mirror wheel 111, a first light source module 113, a second light source module 115 and a controller (not shown). The mirror wheel 111 has a plurality of reflective regions and a plurality of transmissive regions arranged alternately to coordinate with the switching between the first light source module 113 and the second light source module 115. Each of the light source modules 113, 115 comprises a green light-emitting diode (LED), a red LED and a blue LED.
The controller is configured to control the first and the second light source modules 113, 115 to emit light beams according to the first and the second main time sequences to form a first light beam for projecting onto the reflective regions of the mirror wheel 111 and a second light beam for projecting onto the transmissive regions of the mirror wheel 111. The first and the second light beams thus generated then travel via the reflective regions and the transmissive regions of the mirror wheel 111 respectively into the imaging system 13 for imaging.
In the conventional projection apparatus 1, since the mirror wheel 11 is driven by a motor, the apparatus as a whole has an increased volume and generates noise. Furthermore, as a mechanical rotating structure, the mirror wheel 111 delivers a slow switching speed, which causes light dissipation and decreases the instantaneous luminous flux when switching according to the time sequence or in the border regions between the reflective regions and the transmissive regions.
FIG. 2 illustrates another conventional projection apparatus 2 with two light sources. The projection apparatus 2 comprises a light source system 21 and an imaging system 23. The light source system 21, which is adapted to provide light beams necessary for imaging, comprises a first light source (not shown), a second light source (not shown), a color wheel 211, a light source driver 213, a digital micromirror device (DMD) driver 215 and a first DMD 217. The DMD driver 215 is configured to output a first control signal 210a and a second control signal 210b for controlling a plurality of micro mirrors on the first DMD 217 to tilt at a first angle 212a or a second angle 212b respectively.
In response to the first time sequence, the first light source generates a first light beam 214a that is projected onto the first DMD 217. After being reflected by the micro mirrors (not shown) of the first DMD 217 which have been tilted at the first angle 212a, the first light beam 214a then travels through the color wheel 211 before being projected to the imaging system 23. Likewise, in response to the second time sequence, the second light source generates a second light beam 214b that is projected onto the first DMD 217. After being reflected by the micro mirrors of the first DMD 217 which have been tilted at the second angle 212b, the second light beam 214b then travels through the color wheel 211 before being projected to the imaging system 23. In response to the first light beam 214a and the second light beam 214b, a second DMD 231 included in the imaging system 23 then adjusts the micro minors (not shown) thereof respectively to project the images onto a screen 233.
In the prior art, the projection apparatus 2 controls the first DMD 217 to switch between the two light sources according to a signal. As compared to the projection apparatus 1, this delivers a faster switching speed and smaller overall volume. However, compared with other projection apparatuses, the additional first DMD 217 leads to extra light dissipation, resulting in the decrease of the imaging luminance. Moreover, the additional DMD remarkably increases the costs of the apparatus.
It follows from the above description that the existing projection apparatuses either switches between the light sources in a mechanical manner with poor efficiency, or switches between the light sources by using an expensive DMD with decreased luminance and increased costs. Accordingly, it is important to find a way for a projection apparatus with two light sources to be switched quickly while still achieving high reliability, prolonged light source service life and improved imaging luminance. In addition, the projection apparatus should also have a smaller volume, decreased costs and higher imaging quality.